Law mandates the metric system of measurement

According to the Administrative Code of 1987, the metric system of weights and measures shall be used in the Philippines for all products, articles, goods, commodities, materials, merchandise, utilities, services, as well as for commercial transactions like contracts, agreements, deeds and other legal instruments publicly and officially attested, and for all official documents. Only weights and measures of the metric system shall be officially sealed and licensed.

The metric system shall be fully adopted in all agricultural, commercial, industrial, scientific and other sectors. Persons or entities allowed under existing laws to use the English system or other standards and weights are given until the date to be fixed by the Metric System Board to adopt the metric system. (Sections 29-30 of Chapter 8)

"Year" shall be understood to be twelve calendar months; "month" of thirty days, unless it refers to a specific calendar month in which case it shall be computed according to the number of days the specific month contains; "day," to a day of twenty-four hours; and "night," from sunset to sunrise. (Section 31)